Improved link-motion for steam-engines



UNITE@ STATES PATENT OFFICE.

JOHN F. ALLEN, OF NE\V YORK, N. Y.

IMPROVED LINK-MOTION FOR STEAM-ENGINES.

Specication forming part of Letters Patent No. 35,070, dated April 29,1862.

To all whom t may concern:

Be it known that I, JOHN F. ALLEN, of New York, in the county and Stateof New York, have invented a new and useful Improvement in theApplication of the Link-Motion to Steam-Engines, and I do hereby declarethat the following is a full, clear, and exact description thereof,reference being had to the accompanying drawings, and to the charactersof reference marked thereon.

The Stephenson, or, as it is sometimes termed, I-iowe, link-motion hasheretofore generally been applied to steam-engines as a variable cut-offgear to give motion to one or two lap slide-valves, each of whichperforms the several offices of admitting, cutting olf, and releasingsteam to and from the cylinder, and for points of cut off whichcorrespond nearly with the end of the pistons stroke sueh application iseffective, as the valve then receives a quality of motion which allowsitfto perform all its said functions in a proper manner; but when thesaid link-motion in its application as aforesaid is so connected withthe kind of valve specified as to cause the said valve to cut off thesupply of steam atan early period of the pistons stroke, then the actionof the valve in exhausting is suoli that effects arise prejudicial toeconomyin the use of steam, because excessive exhaust lead is producedat the acting end of the cylinder, while at the opposite ornon-actingend excessive cushioning occurs.

It is the object of my invention to produce a more favorable applicationof the link-motion, or an equivalent therefor, to the steamengine, sothat it may effect a short cut-off, and shall also at the same timemaintain a correct exhaust action; and to this end my said inventionconsists in the combination of a Stephenson link-motion, or anequivalent therefor, as hereinafter specified, with one or more steam orinduction valves and one or more exhaust or eduction valves, (the saidsteamv'alves being separate and having different movements from the saidexhaustvalves.) lVhen the exhaust-valves receive mot-ion from that lpartof the rocking lever termed the link, or its equivalent, which is bestsuited to give to them correct action, while the steam-valves are movedby any other part of the same link, which will cause them to effect ashorter cutoff than that part of the link would do by which theexhaustvalves are moved, substant-ially in the manner hereinafter setforth.

To enable others skilled in the art to male use of my invention, I willdescribe a mode of putting it into practice.

In the accompanying drawings, making part of this specification, Figurel shows a side elevation of a steam-engine with the cylinder and itsappendages in section, illustrating my invention; and Fig. 2 shows acrosssection of the link f.

Similar characters of reference denote the same part in both thefigures, in whichct is the main shaft of the engine, on which aresecured two eecentrics, l) and c, which are connected, respectively, bytheir rods d and e with the upper and lower ends of the link f, whichlink is movably sustained at g by the rod h, which swings on the pivott'.

rlhe combination of parts above referred to constitutes what is wellknown as the Stephenson link-motion, the vibratory rocking lever f beingtermed the link v The link j' is slotted or mortised through nearly fromend to end. In this slot are held two sliding blocks, m and n, which canpass each other. (See Fig. 2.)

o is the steam-cylinder, which is shown in section with the steam-chestp and the exhaust chest or passage q.

fr and s are two sliding steam-valves, which, for the rear and frontends of the cylinder, respectively, serve to admit and to cutoff thesupply of steam.

u and r are two sliding exhaust or eduction valves lying in chambers orcavities under the cylinder, each communicating with one of its ends,and these said exhaust-valves alternately op en communication betweeneach end of the cylinder and the exhaust chest or passage q.

The exhaust-valves u and t are connected with and receive motion fromthe block m in the link f through the rod zu, the levers tu and tu?, andthe rod w3, While the steam-valves fr and s are connected with andreceive motion from the block n through the rod t, le vers t and t2, andthe rod 3.

cc is the piston, y the connecting-rod, and 2 the main crank, of theengine, the two parts last mentioned being shown by red lines.

The eccentrics and all the parts which are above specified asconstituting the link-motion may be proportioned and set as in customarypractice, when applied in the ordinary manner. The curvature of the slotin the link f is that of a circular arc described, when the engine is oneither center, from the end of the lever t2 as a center, with the rod t3for a radius.

The steam-valves may be set with the same lap or cover as that of anordinary cup slide-valve,which would be suitable for use with thedescribed link-motion in its usual application, while the exhaust-valveI prefer to 4set without lap, or, in other words, so that thepone valvewill commence to open when the other completes its close.'

I prefer to set the block m near the end of the link f, because thatpart of it will produce in the exhaust-valve (through the said o block mand the connections) movements which will open and close them at timesas nearly coinciding with the terminations of the pistons strokes as maybe desirable.

rlhe block n, from which t-he steam-valves derive their movements, maybe set in any part of the link which will cause them to cut off steam atthe desired point, and because the action of the steam-valves is Whollyindependent of that of the exhaust-valves the eX- tent to whichexpansion may be advantageously carried will notbe limited on account ofincorrect exhaust action being consequent upon a short cut-off.

The block m is made shifting, only so that it may be moved to theextreme opposite end of the link from that in which it is representedwhen it is desired to reverse the motion of the engine, in which casethe block n must also be shifted into the lower half of the link. Thesesaid blocks may each be shifted by the means usually employed for a likepurpose in ordinary applications of a stationary link. Then it is notdesired to have the motion of the engine reversible, the exhaust-valvesmay derive movement from a pin fixed in asolid part of the link f,corresponding` with the face of the block m, while the block n may bemovable in a slot occupying a portion of the upper half of the linkonly; but the steam- Valves may also be moved by a pin fixed in any partof the link, which will eifect cut off at any unalterable point.

I do not wish to be understood that my invention is limited to anapplication of the particular link-motion hereinabove specicallydescribed, as there are other means by which the vibratory rocking leverf may receive the peculiar movements which are imparted to it by the twoeccentrics b and c-as, for example, a single eccentric applied in amanner which is the subj ect of an application for Letters Patent of theUnited States iiled by me simultaneously with the present, and entitledan improvement in the valve-gear of steamengines; and thislast-mentioned improvement, which is a substitute for the Stephensonlink-motion, I have particularly contemplated applying in the mannerwhich is the subject of my invention herein described.

My invention is not limited to any particular mode of connecting thevalves with the link.

I am aware that separate exhaust and steam valves have been adapted tothe cylinders of steam-engines in the manner above described. Itherefore disclaim as new separated steam and exhaust valves when theseare operated by other means than by a single link-motion; but

What I claim as my invention, an d desire to secure by Letters Patent,is-

The combination of a single link-motion, or its equivalent, ashereinbefore specified,with one or more steam-valves and one or moreexhaust-valves, the steam-valves having movements independent of anddifferent from those of the exhaust-valves, When all the said valvesreceive their respective movements from the single link-motionaforesaid, substantially in the manner hereinbefore set forth, for thepurpose specified.

In testimony whereof I have hereunto set my hand this 4th day of April,lSl.

JOHN F. ALLEN.

In presence of- HORACE ANDREWS, C. B. RICHARDS.

